1. Field of the Invention
This invention relates to an image processing apparatus and, more particularly, to an image processing apparatus having a function of adding a particular pattern to a reproduced image.
2. Description of the Related Arts
Copying machines capable of obtaining a multi-color copy having high image quality have been recently developed. The recent improvements in the picture quality of copying machines which now have a color capability have been accompanied by the fear of counterfeiting, in which specific originals such as bank notes and securities, which are not meant to be copied, are duplicated at such a high picture quality that the copies are almost indistinguishable from the originals. However, in the prior art, it was almost impossible to identify the copying machine used for counterfeiting or the user who misused the machine, from the duplicates.
In a case where an original which should not be copied has been copied for improper use, it is important to trace back to the copy user or abused copying machine.
To identify the copying machine used for copying, a method for adding a particular pattern to duplicates is suggested by the present applicant in U.S. Pat. No. 5,257,119, and U.S. Pat. No. 5,363,202.
However, there is the drawback that, if the function for adding a pattern is forged, the method cannot be fully functioned.